A quantitative analysis of the interaction between zidovudine (AZT) and human serum albumin (HSA) was achieved using Isothermal titration calorimetry (ITC) in combination with fluorescence and 1H NMR spectroscopy. ITC directly measure the heat during a biomolecular binding event and gave us thermodynamic parameters and the characteristic association constant. By fluorescence quenching, the binding parameters of AZT-HSA interaction was determined and location to binding site I of HSA was confirmed. Via T1 NMR selective relaxation time measurements the drug-protein binding extent was evaluated as dissociation constants Kd and the involvement of azido moiety of zidovudine in molecular complex formation was put in evidence. All three methods indicated a very weak binding interaction. The association constant determined by ITC (3.58×102M-1) is supported by fluorescence quenching data (2.74×102M-1). The thermodynamic signature indicates that at least hydrophobic and electrostatic type interactions played a main role in the binding process.

This work is focused on self-assembled monolayers (SAMs) fabrication, using two types of Au surfaces, by subsequent attachment of different layers in order to develop a stable platform consisting of covalent multilayer functionalized gold surfaces. The key step in the construction of SAMs is the covalent linkage to the gold surface, via an amino-thiol derivative, of a cyclooctyne unit exhibiting strained triple bonds which react fast (catalysts are not needed) and quantitatively with organic azides and enable the introduction of various chemical functionalized entities on the gold surface. The versatility of the system is demonstrated by the reaction of the cyclooctyne decorated gold surface with an azide functionalized terpyridine followed by step by step complexation with Fe(II) and another terpyridine unit resulting into a multilayer covered gold surface. The Au surfaces were characterized by XPS to determine the chemical composition of the resulting SAMs. SPR was applied for real-time monitoring of the molecular interactions that occurred on the Au surface for each deposited layer. DPN was used to direct pattern the terpyridine-ink on a pre-functionalized AuIDE electrode. The AFM topology resulted from DPN and PEIS demonstrated metal-coordinating ligand of Fe(II)-Terpy.

Assessment of interaction between β-cyclodextrin and 3-carboxy-1-[(2-phenyl-1,3-thiazol-4-yl) methyl]pyridin-1-ium iodide (3CPTMPI) in aqueous solution were investigated by isothermal titration calorimetry (ITC) and 1D and 2D 1H NMR spectroscopy at 298 K. Thermodynamic analysis using ITC revealed that the association constant of β-cyclodextrin and 3CPTMPI is 441.6 M−1 with favorable enthalpy and entropy changes. These thermodynamic parameters indicate that the binding is dominated by hydrophobic interactions, which is in agreement with inclusion complex formation. The details of β-CD/3CPTMPI molecular interaction was analyzed by 1H 2D NMR allowing the proposition of an inclusion model for 3CPTMPI into β-CD. Rotating frame NOE spectroscopy (ROESY) was used to certain the solution geometry host–guest complex. The results reveal that the 3CPTMPI molecule penetrates into β-CD cavity with both aromatic and thiazol rings. For this type of inclusion complex, the association constant K obtained by 1H NMR and ITC are in good agreement and both methods sustain a 1:1 stoichiometry.

The interaction between stavudine, a nucleoside reverse transcriptase inhibitor and human serum albumin (HSA), was investigated by fluorescence quenching technique and isothermal titration calorimetry (ITC). A good linearity of albumin fluorescence quenching in the presence of stavudine was determined. Analyzing these data we obtained for the dissociation constant the value Kd=(18.18±0.46)×10−5M. However, due to contradictory results obtained in ITC experiments, we checked the fluorescence quenching data for the inner-filter effect, the main confounding factor in the observed quenching. Based on the UV–vis absorption data we have corrected the observed fluorescence intensities and concluded, in accordance with ITC results, that stavudine binding to HSA is negligible and the observed quenching effect is entirely caused by a failure to correct for the inner-filter effect.

Promethazine Hydrochloride (PTZ) is an antihistaminic drug widely used in various clinical applications. Due to the fact that PTZ is oxygen sensitive, in many applications it needs to be loaded into an insoluble matrix. Among the drug loading and release matrix, synthetic zeolite 13X is one of the most suitable. In this paper, we performed a study for the drug adsorption/release, using a zeolite matrix. The drug adsorption/release studies have been performed for different PTZ concentrations and different amount of zeolite, using UV-Vis spectroscopy. Langmuir and Freundlich adsorption isotherms were used to correlate the equilibrium adsorption data. Pseudo-first and pseudo-second order kinetic models were applied to describe the adsorption process. The adsorption yield was calculated to be 61.76%. Freundlich isotherm was found to be more suitable for describing the adsorption-desorption equilibrium data of PTZ into zeolites and the kinetic data fitted well the pseudo-second-order model.

The interaction of tolmetin (TOL) with human serum albumin (HSA) in physiological buffer solution (pH 7.4) was studied by fluorescence and UV-vis absorption spectroscopy at different temperatures, combined with time-resolved fluorescence measurements. The experimental results showed that there was a strong fluorescence quenching of HSA by tolmetin. Using the continuous variation method, a single class of binding sites for TOL on HSA was put in evidence. The binding constants Ka were calculated at different temperatures, using a nonlinear fit to the experimental data, and the thermodynamic parameters ΔH(0), ΔS(0) and ΔG(0) were given. The obtained thermodynamic signature suggests that at least van der Waals and electrostatic type interactions are present. Quenching efficiency calculations, based on steady state and time-resolved spectroscopy, indicate that both static and dynamic quenching mechanisms are present.

The adequacy of the effective phase function (EPF) used to describe the light scattered at small angles was tested on aqueous suspensions of polystyrene microspheres. Angular resolved light scattering measurements were performed on two types of latex suspension, which contained polystyrene spheres of 3 mu m and 5 mu m diameters, respectively. The experimental data were fitted with two EPF approximants. If the polystyrene spheres are at least 3 mu m in diameter the quasi-ballistic light scattering process can be described relatively well by the EPF in a small angular range centered in the forward direction. The forward light scattering by macroscopic samples containing microspheres can be modeled relatively well if the true Mie single particle scattering phase function is replaced by a simpler Henyey-Greenstein dependence having the same width at half-height as the first scattering lobe.

Red blood cells (RBCs) in the presence of plasma proteins or other macromolecules have a tendency to form aggregates. Light-scattering technique was used to investigate the RBC aggregation process. A highly diluted suspension of RBCs was illuminated with a 632.8-nm HeNe laser. Angular-resolved measurements of light intensity scattered by an RBC suspension from a 200-microm thick optical glass cuvette during 10 min of their aggregation process were performed at 1 to 4 off-axis deg with a very high angular resolution, at hematocrits in the range of 3.5 x 10(-2) to 10(-1). The angular spreading of forward-scattered light at small angles during the RBC aggregation process was described in terms of a new, effective phase function model that has been used for fitting the experimental data. The aggregated RBCs' optical properties, such as effective scattering anisotropy and scattering cross section, were determined. The results were compared with prediction of Mie theory for equivolumetric spherical particles. The time dependence of the aggregates mean radius and of the mean number of cells per aggregate was also calculated. Last, the potential of the proposed technique (forward-scattering light technique) as a new quantitative investigation of cellular aggregation process was estimated.